JdcTypeR

iTrader: (19)

I have a 2004 Audi A3 2.0 FSI and the fuel pump keeps running with the ignition off. The only way to stop this is by removing fuse 27.
I have to codes which may or may not be related -P0091 valve for metering short to ground lower limit reached intermittant and -P2540 low pressure fuel sensor implausible signal not a plausible signal.
I decided to look at the fuel pump issue first and there is a permanent live and earth to the pump after the fuel control module.
I disconnected the drivers door harness to see if it stopped but it didn't. I removed all wires from the fuel control module other than the main live and earth and it still runs.
Do these have a fuel pump relay as i can't seem to find it and the wiring diagram i have does not show one or is it all controlled by the fuel control module?
Thanks
James

cuprajake

iTrader: (11)

Join the Tfsi tuning group on Facebook. There are some very knowledgeable people on there.

JdcTypeR

iTrader: (19)

Thankyou! I did join a vw/audi forum but not one single reply lol.
I'll give the facebook group a go

cuprajake

iTrader: (11)

You have tuners on there and also Alex from aks. All know there stuff

thenewgalaxy

Ali B on here would be worth a shout if you get stuck, I think he knows a thing or two about VAGs

JdcTypeR

iTrader: (19)

Thanks for that!

ALi-B

iTrader: (1)

The fuel pump control module is for all intents the relay. Relays for switching small loads are a thing of the past; its all solid state these days (not even the indicators)

These cars (like many modern cars) have variable speed fuel pumps to vary the fuel pressure, the pump control unit is what does this job. The pump controller will be activated by the central electronics module (which turns it on for a few seconds when you open the driver's door, and probably turns it off if the airbags are triggered) and the Engine ECU. The Engine ECU controls the pump speed via a pressure sensor somewhere on the high pressure pump (thats the pump fitted on the engine, not the one in the tank).

I have no wiring diagrams on these...scarce stuff on modern VAGs without elsawin/erwin

The low pressure sensor is a known fault. BUT this is only when the ignition is on or engine is running. So your P2540 code is probably due to the pump running at full tilt making the fuel pressure too high (hence not plausible). Live data should show this to be 4 to 5 bar with the engine at idle IIRC.

If you have cut/disconnected the signaling wires at the pump control unit above the tank, then unless it has some bizarre fail-safe (i.e run the pump if it loses connection), then its probably the pump control module that has failed closed-circuit.

JdcTypeR

iTrader: (19)

Thankyou for your reply.
That is what im thinking that the fuel pump control module is at fault.
Before the car came to me it had a low pressure intank pump and a new low pressure fuel sensor.
The car wont rev past 3000rpm then all of a sudden it will which i suspect is because the low pressure fuel supply is not being regulated by the fuel control module?

JdcTypeR

iTrader: (19)

I thought I'd update this.
A new fuel control module sorted the fuel pump problem of constantly running but it still wouldn't rev over 3000rpm.

Checked all the fuel related sensors which were fine as fuel pressure was too low.
Replaced the high pressure pump and that sorted it
Thanks for the help previously.
cheers
James

stiscooby

Rather than starting a new thread I thought I would ask a question in here as it's another Audi Tech question....

I have an 2006 A3 2.0 TFSI which occasionally has the ESP and steering wheel light display on the dash when cornering. When this happens power steering still works but when you let go of the wheel, rather than it slowly rotating back to centre it just stays where it is.

If the car is then turned off/back on again the lights go out.

I have today had the car MOT'd so while at a local garage (not an Audi stealer) they checked the fault code and it is reporting code 778 - steering angle sensor. I was told they checked this with the Audi stealer who confirmed the fault code is correct and will mean a new steering rack is needed as the sensor is built in - at a cost of £800 just for parts!

I have been searching on line but can't really find too much about it. Does anyone know if a new rack is required or could it be something else? Some things I have found seem to report the sensor is behind the steering wheel itself??

Any advice much appreciated.

Thanks

ALi-B

iTrader: (1)

778 isn't the proper/full code, alot of generic diagnostic kit will miss off the full translation of the fault code. So all you have there is its the steering angle sensor, not the full explanation of whats wrong with it (adaption, implausible signal, open circuit, short circuit etc):

For example: http://wiki.ross-tech.com/wiki/index.php/00778

A proper diagnostic report will also include the code of component part at fault...like G85. If its reporting G85 at fault, then as far as I know, the G85 sensor on a 8P platform VAG (A3/MKV Golf/Leon etc) is NOT in the rack (its part of the slip ring on the steering column -be careful, it also works the airbag).

Anyhoo as a starting point:

Is your steering wheel straight when driving? If not, the ESP will throw a tissy fit. Usually you get this problem when someone replaces the track-rod ends and fudges up the tracking/toe.

TBH to go any further, I'd suggest you find someone local with VAG-COM/VCDS as that will give you far more accurate fault code. You may find someone on the VW/Audi/Seat/Skoda forums who can help with this (but for gods sake don't post up you have a 778 code like here, because they'll rip you shreds without posting a complete VAG-COM vehicle scan -those forums tend to have rules about how to post fault codes, so you have been warned).

stiscooby

Ali-B - Thank for the info! ;-)

Haven't come across VAG-COM before but doing a search I gather it's diagnostic software people can use. Might have to see if I can find anyone in the area who could help me out as I don't fancy spending a few hundred quid on that.

As it happens I dropped my car into my Audi dealer today for them to reset my service indicator as when it was last there for a long life/2 year service last year it's now reporting it needed another one, 12 month/5k miles later, so they only re-set it for a 12 month period..... anyway, while there I asked them about the fault code and they didn't seem too interested apart from saying (as you have also mentioned) although the fault code is reported there could be something else actually causing the fault and for them to do anything I would have to book it in for them to carry out further tests for half hour or so and will cost me £75!

The wheel is straight and there have been no knocks or work carried out on the car at all so I don't believe anything to be out of alignment etc. Tyre's are also in good condition too.

Will see if I can find anyone in the area with better diagnostic software, failing that I might have to just stump up the cash at Audi for them to give a detailed report on the fault as the place I took it to is just a general garage so their equipment doesn't possibly give the full detail of whats causing the sensor to kick in/flag a fault.

Thanks for the heads up on the Audi forums, as it happens I have also posted on a few and not been ripped to shreds yet!